<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>10-if判断成绩</title>
</head>
<body>
    <script>
        let chengji = +prompt('输入成绩')
        if(chengji >= 90){
            alert('优秀')
        }else if(chengji >= 70 && chengji <= 90){
            alert('良好')
        }else if(chengji >= 60 && chengji <= 70){
            alert('及格')
        }else{
            alert('不及格')
        }
    </script>
</body>
</html>100